The primary objective of this study is to determine if omega-3 polyunsaturated fatty acids reduce atrial fibrillation and other outcomes after cardiac surgery. In this placebo-controlled trial, patients undergoing elective coronary artery bypass graft surgery with or without valve repair will be treated with omega-3 polyunsaturated fatty acids perioperatively. The following hypotheses will be tested: 1. omega-3 polyunsaturated fatty acids reduces the incidence of atrial fibrillation (AF) after cardiac surgery, 2. omega-3 polyunsaturated fatty acids, administered in the perioperative period for cardiac surgery, decreases postoperative complication rates, and 3. omega-3 polyunsaturated fatty acids decrease intensive care unit and hospital length-of-stay.